The present invention relates generally to the lowering, raising, and control of the temperature of the human body. More particularly, the invention relates to a method and intravascular apparatus for controlling the temperature of the human body.
Background Informationxe2x80x94Organs in the human body, such as the brain, kidney and heart, are maintained at a constant temperature of approximately 37xc2x0 C. Hypothermia can be clinically defined as a core body temperature of 35xc2x0 C. or less. Hypothermia is sometimes characterized further according to its severity. A body core temperature in the range of 33xc2x0 C. to 35xc2x0 C. is described as mild hypothermia. A body temperature of 28xc2x0 C. to 32xc2x0 C. is described as moderate hypothermia. A body core temperature in the range of 24xc2x0 C. to 28xc2x0 C. is described as severe hypothermia.
Hypothermia is uniquely effective in reducing ischemia. For example, it is effective in reducing brain injury caused by a variety of neurological insults and may eventually play an important role in emergency brain resuscitation. Experimental evidence has demonstrated that cerebral cooling improves outcome after global ischemia, focal ischemia, or traumatic brain injury. For this reason, hypothermia may be induced in order to reduce the effect of certain bodily injuries to the brain as well as ischemic injuries to other organs.
The apparatus of the present invention can include a heat transfer element which can be used to apply cooling to the blood flowing in a vessel. The heat transfer element, by way of example only, comprises first and second elongated, articulated segments, each segment having a turbulence-inducing exterior surface. A flexible joint can connect the first and second elongated segments. An inner coaxial lumen may be disposed within the first and second elongated segments and is capable of transporting a working fluid to a distal end of the first elongated segment. In addition, the first and second elongated segments may have a turbulence-inducing interior surface for inducing turbulence within the pressurized working fluid. The turbulence-inducing exterior surface may be adapted to induce turbulence within a free stream of blood flow when placed within an artery or vein. The turbulence-inducing exterior surface may be adapted to induce a turbulence intensity greater than 0.05 within a free stream blood flow. In one embodiment, the flexible joint comprises a bellows section which also allows for axial compression of the heat transfer element.
In an embodiment, the turbulence-inducing exterior surfaces of the heat transfer element comprise one or more helical ridges. Adjacent segments of the heat transfer element can be oppositely spiraled to increase turbulence. For instance, the first elongated heat transfer segment may comprise one or more helical ridges having a counter-clockwise twist, while the second elongated heat transfer segment comprises one or more helical ridges having a clockwise twist. Alternatively, of course, the first elongated heat transfer segment may comprise one or more clockwise helical ridges, and the second elongated heat transfer segment may comprise one or more counter-clockwise helical ridges. The first and second elongated, articulated segments may be formed from highly conductive materials.
The heat transfer device may also have a coaxial supply catheter with an inner catheter lumen coupled to the inner coaxial lumen within the first and second elongated heat transfer segments. A working fluid supply configured to dispense the pressurized working fluid may be coupled to the inner catheter lumen. The working fluid supply may be configured to produce the pressurized working fluid at a temperature of about 0xc2x0 C. and at a pressure below about 5 atmospheres of pressure. The working fluid may be isolyte, saline, D5W, etc.
In yet another alternative embodiment, the heat transfer device may have three or more elongated, articulated, heat transfer segments having a turbulence-inducing exterior surface, with additional flexible joints connecting the additional elongated heat transfer segments. In one such embodiment, by way of example, the first and third elongated heat transfer segments may comprise clockwise helical ridges, and the second elongated heat transfer segment may comprise one or more counter-clockwise helical ridges. Alternatively, of course, the first and third elongated heat transfer segments may comprise counter-clockwise helical ridges, and the second elongated heat transfer segment may comprise one or more clockwise helical ridges.
The turbulence-inducing exterior surface of the heat transfer element may optionally include a surface coating or treatment to inhibit clot formation.
The present invention also envisions a method of cooling the body which comprises inserting a flexible, conductive cooling element into the inferior vena cava from a distal location, and providing a means of warming the body to prevent shivering by means of a cooling blanket. The method further includes circulating a working fluid through the flexible, conductive cooling element in order to lower the temperature of the body. The flexible, conductive heat transfer element absorbs more than about 25, 50 or 75 Watts of heat.
The method may also comprise inducing turbulence within the free stream blood flow within an artery or vein. In one embodiment, the method includes the step of inducing blood turbulence with a turbulence intensity greater than about 0.05 within the vascular system. The circulating may comprise inducing mixing flow of the working fluid through the flexible, conductive heat transfer element. The pressure of the working fluid may be maintained below about 5 atmospheres of pressure.
The cooling or warming may comprise circulating a working fluid in through an inner lumen in the catheter and out through an outer, coaxial lumen. In one embodiment, the working fluid remains a liquid throughout the cycle. The working fluid may be aqueous.
The present invention also envisions a cooling or warming catheter comprising a catheter shaft having first and second lumens therein. The catheter also comprises a cooling or warming tip adapted to transfer heat to or from a working fluid circulated in through the first lumen and out through the second lumen, and turbulence-inducing structures on the tip capable of inducing free stream turbulence when the tip is inserted into a blood vessel. The tip may be adapted to induce turbulence within the working fluid. The catheter is capable of removing at least about 25 Watts of heat from an organ when inserted into a vessel supplying that organ, while cooling the tip with a working fluid that remains a liquid in the catheter. Alternatively, the catheter is capable of removing at least about 50 or 75 Watts of heat from an organ when inserted into a vessel supplying that organ, while cooling the tip with an aqueous working fluid.
In another embodiment, a cooling or warming catheter may comprise a catheter shaft having first and second lumens therein, a cooling or warming tip adapted to transfer heat to or from a working fluid circulated in through the first lumen and out through the second lumen, and turbulence-inducing structures on the tip capable of inducing turbulence when the tip is inserted into a blood vessel.
The present invention may also provide a temperature control apparatus comprising a flexible catheter which can be inserted through the vascular system of a patient to an artery or vein, with an inflatable balloon heat exchanger near the distal end of the catheter. The present invention also encompasses a method for using such a device to perform cooling, heating, or temperature management. After placement in a vessel, an embodiment of the invention includes an apparatus where the heat exchanger balloon is inflated by pressurization with a working fluid, such as saline, isolyte, D5W, or other similar fluids, or combinations of these, via a supply lumen in the catheter. The heat exchanger balloon has one or more blood passageways passing through it, from a proximal aspect of the balloon to a distal aspect of the balloon. When the heat exchanger balloon is inflated to contact the wall of the artery in which it is placed, each of the blood passageways comprises a tube having an inlet in one face of the heat exchanger balloon and an outlet in another face of the heat exchanger balloon, thereby allowing blood to continue flowing through the artery after inflation of the balloon. The blood passageway tubes can be constructed of a material having a relatively high thermal conductivity, such as a thin metallized polymer, such as a film with one or more metallized surfaces. Alternatively, the blood passageway tubes can be constructed of a metal-loaded polymer film. Further, the entire heat exchanger balloon can be constructed of such a material, in order to maximize the cooling capacity of the heat exchanger.
After inflation of the heat exchanger balloon, the saline solution, which is chilled by an external chiller, continues circulating through the interior of the heat exchanger balloon, around the blood passageway tubes, and back out of the balloon through a return lumen in the catheter. This cools the blood passageway tubes, which in turn cool the blood flowing through them. This cooled blood then flows through the selected organ and cools the organ.
The device can also incorporate a lumen for a guidewire, facilitating the navigation of the catheter through the vascular system of the patient.
In one aspect, the invention is directed to a catheter system to change the temperature of blood by heat transfer to or from a working fluid. The system includes an inflatable inlet lumen and outlet lumen. The outlet lumen is coupled to the inlet lumen so as to transfer working fluid between the two. The outlet lumen has a structure when inflated to induce turbulence in the blood and/or in the working fluid.
Variations of the system may include one or more of the following. The inlet lumen and the outlet lumen may be made of a flexible material such as latex rubber. The outlet lumen may have a structure to induce turbulence in the working fluid when inflated, such as a helical shape which may be tapered in a segmented or non-segmented manner. The radii of the inlet and outlet lumens may decrease in a distal direction such that the inlet and outlet lumens are tapered when inflated. A wire may be disposed in the inlet or outlet lumens to provide shape and strength when deflated.
The thickness of the outlet lumen, when inflated, may be less than about xc2xd mil. The length of the inlet lumen may be between about 5 and 30 centimeters. If the outlet lumen has a helical shape, the diameter of the helix may be less than about 8 millimeters when inflated. The outer diameter of the helix of the outlet lumen, when inflated, may be between about 2 millimeters and 8 millimeters and may taper to between about 1 millimeter and 2 millimeters. In segmented embodiments, a length of a segment may be between about 1 centimeter and 10 centimeters. The radii of the inlet and outlet lumens when inflated may be between about 0.5 millimeters and 2 millimeters.
The outlet lumen may further include at least one surface feature and/or interior feature, the surface feature inducing turbulence in the fluid adjacent the outlet lumen and the interior feature inducing turbulence in the working fluid. The surface feature may include one or more helical turns or spirals formed in the outlet lumen. Adjacent turns may employ opposite helicity. Alternatively or in combination, the surface feature may be a series of staggered protrusions formed in the outlet lumen.
The turbulence-inducing outlet lumen may be adapted to induce turbulence when inflated within a free stream of blood when placed within an artery. The turbulence intensity may be greater than about 0.05. The turbulence-inducing outlet lumen may be adapted to induce turbulence when inflated throughout the period of the cardiac cycle when placed within an artery or during at least 20% of the period.
The system may further include a coaxial supply catheter having an inner catheter lumen coupled to the inlet lumen and a working fluid supply configured to dispense the working fluid and having an output coupled to the inner catheter lumen. The working fluid supply may be configured to produce a pressurized working fluid at a temperature of between about xe2x88x923xc2x0 C. and 36xc2x0 C. and at a pressure below about 5 atmospheres of pressure. Higher temperatures may be employed if blood heating is desired.
The turbulence-inducing outlet lumen may include a surface coating or treatment such as heparin to inhibit clot formation. A stent may be coupled to the distal end of the inlet lumen. The system may be employed to cool or heat volumes of tissue rather than blood.
In embodiments employing a tapered helical outlet lumen, the taper of the outlet lumen allows the outlet lumen to be placed in an artery having a radius less than the first radius. The outlet lumen may be tapered in segments. The segments may be separated by joints, the joints having a radius less than that of either adjacent segment.
In another aspect, the invention is directed to a method of changing the temperature of blood by heat transfer. The method includes inserting an inflatable heat transfer element into an artery or vein and inflating the same by delivering a working fluid to its interior. The temperature of the working fluid is generally different from that of the blood. The method further includes inducing turbulence in the working fluid by passing the working fluid through a turbulence-inducing path, such that turbulence is induced in a substantial portion of a free stream of blood. The inflatable heat transfer element may have a turbulence-inducing structure when inflated.
In another aspect, the invention is directed towards a method of treating the brain which includes inserting a flexible heat transfer element into an artery from a distal location and circulating a working fluid through the flexible heat transfer element to inflate the same and to selectively modify the temperature of an organ without significantly modifying the temperature of the entire body. The flexible, conductive heat transfer element preferably absorbs more than about 25, 50 or 75 watts of heat. The artery may be the common carotid or a combination of the common carotid and the internal carotid.
In another aspect, the invention is directed towards a method for selectively cooling an organ in the body of a patient which includes introducing a catheter into a blood vessel supplying the organ, the catheter having a diameter of 5 mm or less, inducing free stream turbulence in blood flowing over the catheter, and cooling the catheter to remove heat from the blood to cool the organ without substantially cooling the entire body. In one embodiment, the cooling removes at least about 75 watts of heat from the blood. In another embodiment, the cooling removes at least about 100 watts of heat from the blood. The organ being cooled may be the human brain.
The circulating may further include passing the working fluid in through an inlet lumen and out through an outlet, coaxial lumen. The working fluid may be a liquid at or well below its boiling point, and furthermore may be aqueous.
Advantages of the invention include one or more of the following. The design criteria described above for the heat transfer element: small diameter when deflated, large diameter when inflated, high flexibility, and enhanced heat transfer rate through increases in the surface of the heat transfer element and the creation of turbulent flow, facilitate creation of a heat transfer element which successfully achieves selective organ cooling or heating. Because the blood is cooled intravascularly, or in situ, problems associated with external circulation of the blood are eliminated. Also, only a single puncture and arterial vessel cannulation are required which may be performed at an easily accessible artery such as the femoral, subclavian, or brachial arteries. By eliminating the use of a cold perfusate, problems associated with excessive fluid accumulation are avoided. In addition, rapid cooling to a precise temperature may be achieved. Further, treatment of a patient is not cumbersome and the patient may easily receive continued care during the heat transfer process. The device and method may be easily combined with other devices and techniques to provide aggressive multiple therapies. Other advantages will
The present invention involves a device for heating or cooling a surrounding fluid in a blood vessel that addresses and solves the problems discussed above. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior, an elongated supply lumen adapted to deliver a working fluid to the interior of the heat transfer element and having a hydraulic diameter, an elongated return lumen adapted to return a working fluid from the interior of the heat transfer element and having a hydraulic diameter, and wherein the ratio of the hydraulic diameter of the return lumen to the hydraulic diameter of the supply lumen is substantially equal to 0.75.
Implementations of the above aspect of the invention may include one or more of the following. The supply lumen may be disposed substantially within the return lumen. One of the supply lumen and return lumen may have a cross-sectional shape that is substantially luniform. One of the supply lumen and the return lumen has a cross-sectional shape that is substantially annular. The supply lumen has a general cross-sectional shape and the return lumen has a general cross-sectional shape different from the general cross-sectional shape of the supply lumen. The catheter assembly includes an integrated elongated bi-lumen member having a first lumen adapted to receive a guide wire and a second lumen comprising either the supply lumen or the return lumen. The bi-lumen member has a cross-sectional shape that is substantially in the shape of a figure eight. The first lumen has a cross-sectional shape that is substantially circular and the second lumen has a cross-sectional shape that is substantially annular. The heat transfer element includes means for inducing mixing in a surrounding fluid. The device further includes means for inducing wall jets or means for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid. The heat transfer element includes an interior distal portion and the supply lumen includes first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior of the heat transfer element at one or more points point proximal to the distal portion of the heat transfer element.
Another of the invention involves a catheter assembly capable of insertion into a selected blood vessel in the vascular system of a patient. The catheter assembly includes an elongated catheter body including an operative element having an interior at a distal portion of the catheter body, an elongated supply lumen adapted to deliver a working fluid to the interior of the distal portion and having a hydraulic diameter, an elongated return lumen adapted to return a working fluid from the interior of the operative element and having a hydraulic diameter, and wherein the ratio of the hydraulic diameter of the return lumen to the hydraulic diameter of the supply lumen being substantially equal to 0.75.
Any of the implementations described above with respect to one aspect of the invention may also apply to other aspects of the invention. Further, implementations of the invention may include one or more of the following. The operative element may include a heat transfer element adapted to transfer heat to or from the working fluid. The heat transfer element may include means for inducing mixing in a surrounding fluid. The operative element may include a catheter balloon adapted to be inflated with the working fluid.
Another aspect of the invention involves a device for heating or cooling a surrounding fluid in a vascular blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior, an integrated elongated bi-lumen member located within the catheter body and including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element, and a third lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element.
Implementations of the invention may include one or more of the following. The catheter body includes an internal wall and the integrated bi-lumen member includes an exterior wall, and the third lumen is substantially defined by the internal wall of the catheter body and the exterior wall of the bi-lumen member. Both the catheter body and the bi-lumen member are extruded. The bi-lumen member is disposed substantially within the third lumen. The second lumen has a cross-sectional shape that is substantially luniform. The third lumen has a cross-sectional shape that is substantially annular. The second lumen has a general cross-sectional shape and the third lumen has a general cross-sectional shape different from the general cross-sectional shape of the second lumen. The bi-lumen member has a cross-sectional shape that is substantially in the shape of a figure eight. The first lumen has a cross-sectional shape that is substantially circular and the second lumen has a cross-sectional shape that is substantially luniform. The heat transfer element includes means for inducing mixing in a surrounding fluid. The device further includes means for inducing wall jets or means for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid. The heat transfer element includes an interior distal portion and the supply lumen includes first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior of the heat transfer element at one or more points point proximal to the distal portion of the heat transfer element.
Another aspect of the present invention involves a catheter assembly capable of insertion into a selected blood vessel in the vascular system of a patient. The catheter assembly includes an elongated catheter body including an operative element having an interior at a distal portion of the catheter body, an integrated elongated bi-lumen member located within the catheter body and including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to the interior of the operative element or a return lumen to return a working fluid from the interior of the operative element, and a third lumen within the catheter body and comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element.
Another aspect of the invention involves a method of manufacturing a catheter assembly for heating or cooling a surrounding fluid in a blood vessel. The method involves extruding an elongated catheter body; locating a heat transfer element including an interior at a distal portion of the catheter body; extruding an integrated elongated bi-lumen member including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element; and providing the integrated bi-lumen member substantially within the elongated catheter body so that a third lumen is formed, the third lumen comprising either a supply lumen to deliver a working fluid to an interior of the heat transfer element or a return lumen to return a working fluid from the interior of the heat transfer element.
Implementations of the invention may include one or more of the following. The second lumen has a hydraulic diameter and the third lumen has a hydraulic diameter, and the ratio of the hydraulic diameter of the second lumen to the hydraulic diameter of the third lumen is substantially equal to 0.75. The step of providing the integrated bi-lumen member substantially within the elongated catheter body includes simultaneously extruding the integrated bi-lumen member substantially within the elongated catheter body.
Another aspect of the present invention involves a method of manufacturing a catheter assembly. The method includes extruding an elongated catheter body; locating an operative element including an interior at a distal portion of the catheter body; extruding an integrated elongated bi-lumen member including a first lumen adapted to receive a guide wire and a second lumen, the second lumen comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element; and providing the integrated bi-lumen member substantially within the elongated catheter body so that a third lumen is formed, the third lumen comprising either a supply lumen to deliver a working fluid to an interior of the operative element or a return lumen to return a working fluid from the interior of the operative element.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment and a second heat transfer segment, and at least one elongated supply lumen located within the catheter body, the at least one elongated supply lumen including first means for delivering working fluid to the interior distal portion of the first heat transfer segment and second means for delivering working fluid to the interior portion of the second heat transfer segment.
In an implementation of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion, and at least one elongated supply lumen located within the catheter body, the at least one elongated supply lumen including first means for delivering working fluid to the interior distal portion of the heat transfer element and second means for delivering working fluid to the interior portion of the heat transfer element at one or more points proximal to the distal portion of the heat transfer element.
In an implementation of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment and a second heat transfer segment, a first elongated supply lumen located within the catheter body and terminating at the interior distal portion of the heat transfer element into first means for delivering working fluid to the interior distal portion of the heat transfer element, and a second elongated supply lumen located within the catheter body and terminating at a point proximal to the distal portion of the heat transfer element into second means for delivering working fluid to the interior portion of the heat transfer element at a point proximal to the distal portion of the heat transfer element.
In an implementation of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior distal portion and an interior portion defining at least a first heat transfer segment interior portion and a second heat transfer segment interior portion, a first elongated supply lumen located within the catheter body and terminating at the interior distal portion of the first heat transfer segment into first means for delivering working fluid to the interior of the first heat transfer segment, and a second elongated supply lumen located within the catheter body and terminating at a point proximal to the distal portion of the heat transfer element into second means for delivering working fluid to the interior portion of the second heat transfer segment.
In an implementation of the invention, the second working fluid delivering means is adapted to deliver working fluid to the interior portion of the heat transfer element near a midpoint of the heat transfer element.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, the heat transfer element including at least a first heat transfer segment, a second heat transfer segment, and an intermediate segment between the first heat transfer segment and the second heat transfer segment, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, the supply lumen member including a circular outer surface, an elongated return lumen defined in part by the outer surface of the supply lumen member and the interior portion of the heat transfer element and adapted to return the working fluid from the interior of the heat transfer element, and wherein the distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the intermediate segment is less than the distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the first heat transfer segment.
Implementations of the invention may include one or more of the following. The distance between the interior portion of the heat transfer element and the outer surface of the supply lumen member adjacent the intermediate segment is such that the characteristic flow resulting from a flow of working fluid is at least of a transitional nature. The intermediate segment includes an interior diameter that is less than the interior diameter of the first heat transfer segment or the second heat transfer segment. The supply lumen member includes an outer diameter adjacent the intermediate segment that is greater than its outer diameter adjacent the first heat transfer segment or the second heat transfer segment. The supply lumen member comprises a multiple-lumen member. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to 0.75 the hydraulic diameter of the supply lumen. The intermediate segment includes a flexible bellows joint.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and means located within the heat transfer element for further enhancing mixing of the working fluid to effect further heat transfer between the heat transfer element and working fluid.
Implementations of the invention may include one or more of the following. The supply lumen member comprises a multiple-lumen member having a circular outer surface. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to 0.75 of the hydraulic diameter of the supply lumen.
Another aspect of the present invention involves a device for heating or cooling a surrounding fluid in a blood vessel. The device includes an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and a mixing-enhancing mechanism located within the heat transfer element and adapted to further mix the working fluid to effect further heat transfer between the heat transfer element and working fluid.
Implementations of the invention may include one or more of the following. The supply lumen member comprises a multiple-lumen member having a circular outer surface. The supply lumen member includes a supply lumen having a hydraulic diameter and the return lumen has a hydraulic diameter substantially equal to the hydraulic diameter of the supply lumen. A fourteenth aspect of the present invention involves a method of heating or cooling a surrounding fluid in a blood vessel. The method includes providing a device for heating or cooling a surrounding fluid in a blood vessel within the blood stream of a blood vessel, the device including an elongated catheter body, a heat transfer element located at a distal portion of the catheter body and including an interior portion adapted to induce mixing of a working fluid to effect heat transfer between the heat transfer element and working fluid, an elongated supply lumen member located within the catheter body and adapted to deliver the working fluid to the interior of the heat transfer element, an elongated return lumen member located within the catheter body and adapted to return the working fluid from the interior of the heat transfer element, and a mixing-enhancing mechanism located within the heat transfer element and adapted to further mix the working fluid to effect further heat transfer between the heat transfer element and working fluid; causing a working fluid to flow to and along the interior portion of the heat transfer element of the device using the supply lumen and return lumen; facilitating the transfer of heat between the working fluid and the heat transfer element by effecting mixing of the working fluid with the interior portion adapted to induce mixing of a working fluid; facilitating additional transfer of heat between the working fluid and the heat transfer element by effecting further mixing of the working fluid with the interior portion with the mixing-enhancing mechanism; causing heat to be transferred between the blood stream and the heat transfer element by the heat transferred between the heat transfer element and working fluid.